A posting on social media that led some people to assume there would be a shooting Monday, Oct. 1, at Sierra Vista High School in Baldwin Park was unfounded, police said.

Officers interviewed but didn’t arrest a 17-year-old boy who allegedly posted “all of u will be sorry” with an emoji of a green water pistol on Instagram. Police said the teen used the name of another student.

“The investigation shows the postings were an ill-conceived senior prank,” Baldwin Park Police Chief Mike Taylor said in a statement, adding that detectives will review the case with the Los Angeles County District Attorney’s Office to decide if any charges will be filed.

Froilan N. Mendoza, superintendent at Baldwin Park Unified, said the student is no longer on the campus and the district will take appropriate disciplinary measures.

He said Baldwin Park police notified the district about the message around 1 p.m. Sunday, Sept. 30. Mendoza called it an inappropriate message and pointed out that it never mentioned the school’s name.

The posting appeared Sunday on Instagram. The 17-year-old created an Instagram account using the name of another student, Lt. Chris Kuberry said.

“The student whose name it was posted in had nothing to do with it,” Kuberry said.

As others spread the posting on social media, Kuberry said it took a life of its own and people started mentioning Sierra Vista High School and that someone is threatening to shoot up the school.

Classes weren’t cancelled Monday.

“Out of an abundance of caution, the district heightened security measures at the site,” the Baldwin Park Unified School District said in a statement.

Ruby Gonzales started working for the company in 1991. Since then she has written about cities, school districts, crimes, cold cases, courts, the San Gabriel River, local history, anime, insects, forensics and the early days of the Internet when people still referred to it as the "information superhighway." Her current beat includes breaking news, crimes and courts for the San Gabriel Valley Tribune, Pasadena Star News and Whittier Daily News. When not in crime reporter mode, she frequents the remaining bookstores in the San Gabriel Valley, haunts craft stores or gets dragged to eateries by a relative who is a foodie.